It should be understood that the term "mobile station" used throughout the specification includes mobile telecommunications units that communicate with a base station in a wireless telecommunications network by means of electromagnetic waves such as mobile wireless telephones and cellular telephones that are designed to exchange voice information with a base station. The term includes mobile data communication devices such as pagers and facsimile machines for exchanging data. The term mobile station also includes hybrid devices such as personal communications systems (PCS) that have both telephone and data communications features.
New digital cellular systems, commonly known as Personal Communications Systems (PCS) have recently been introduced in North America. PCS operates at a frequency band of about 1850 to 1990 Mhz so as not to interfere with the existing cellular frequency band of about 800 to 900 Mhz. PCS provides enhanced features compared to existing cellular systems, such as short message service (SMS), voice mail, call forwarding, over the air activation (OTA), and other features. There are also digital cellular telephones operating under CDMA digital systems and further digital systems operating at 800 Mhz frequency.
Digital mobile stations can be activated over the air using short message service. A purchaser of a mobile station can leave the store without having the phone activated. When the mobile station is turned on by the purchaser, the mobile station sends a registration message with an inactive MIN (mobile identity number) to the serving mobile switching center serving the mobile station. The MSC recognizes the mobile station as a non-programmed mobile station and routes the message to the over the air activation processor. The information forwarded to the over the air activation processor further includes additional information contained in the registration message such as the electronic serial number (ESN) of the mobile station. This allows the over the air activation processor to assign the activation parameters to the mobile station and send these parameters back to the mobile station using the inactive MIN. These activation parameters typically include the number assignment module (NAM) designation parameters. The NAM parameters typically include the system identification, telephone number, access overhead class, group identification, initial paging channel, security lock code, local use flag, A/B system selection, and new mobile identity number (MIN).
To protect the subscriber or mobile station from being activated with incorrect information from a third party operator, a security lock code, known to the home operator, is assigned to the mobile station. When a mobile is requested to provide information of its NAM or to download its NAM, the mobile station requests a challenge of the network for the network to supply knowledge of the mobile station's security lock before allowing the new activation parameters to be read or downloaded. However, within the network there does not presently exist any mechanism to process the challenge request made by the mobile station. Accordingly, there is a need for a standard implementation that permits a mechanism to transmit the challenge request with the appropriate data and allow specialized centers within the network to perform the challenge for subsequent validation by the mobile station.